1. Technical Field
The present disclosure relates to spark plugs.
2. Related Art
A spark plug is known in which an electrode tip is joined in a center electrode or a ground electrode (either of which may be hereafter referred to simply as “an electrode”) (see JP Patent No. 4705129, for example). The electrode tip (hereafter referred to as “a noble metal tip”) is formed from a noble metal (such as platinum, iridium, ruthenium, or rhodium) having excellent spark erosion resistance and oxidation resistance, or an alloy composed chiefly of a noble metal. Generally, the noble metal tip is joined in a base material (an electrode or an intermediate member for joining with the electrode) by laser welding. Specifically, the noble metal tip is joined to the base material by irradiating the noble metal tip with laser along an outer periphery thereof.
As other relevant literature, JP-A-2002-93547, JP-A-2005-183167, JP-A-2007-87969, and JP-A-2005-50732 may be cited.